Hoists which ride on ceiling-mounted or other tracks are commonly used in hospitals and other care centers, as well as in the homes of those with mobility impairments, to convey people and/or equipment to different areas (e.g., from a bed to a bathroom). Examples of such hoists are provided, for example, in U.S. Pat. No. 7,237,491 to Faucher et al., International (PCT) Patent Appln. Publication WO 88/09159, and in other patents cited in (and citing to) these references. Such hoists are usually electrically-powered, and they may ride on the tracks via manually-driven trolleys, or trolleys which are themselves electrically driven to assist in driving the hoists along their tracks. Power may be provided to the hoists via elongated flexible cables that follow the hoists along their tracks, but these can cause difficulties owing to the length of cable needed where the hoists are to travel long distances, and owing to the desire to avoid cable slack and dangling cable. Hoists have also been developed which are powered by rechargeable batteries, with the batteries being recharged when the hoist is placed at a docking position near the end of a track (or at any one of several docking positions along the track). These too pose difficulties in that users often forget to place the hoists back in their docking positions after use, leading to dead batteries and hoists which are inoperative until they are recharged (which can lead to hardships for their users). Some hoists have a feature wherein their trolleys automatically drive the hoists to a charging station when not in use, thereby better ensuring that their batteries remain charged. However, such “return-to-charger” features are sometimes thwarted when objects (such as curtains, IV equipment, monitors, etc.) obstruct the return paths of the hoists. Additionally, return-to-charger features cannot easily be implemented in “moving-track” systems such as the ones shown in U.S. Pat. No. 7,237,491, wherein the track on which the hoist rides itself rides on another track (e.g., a first track aligned along one direction is relocatable on a second track oriental perpendicularly from the first track). In such systems, the hoist can move in a variety of directions (e.g., about a plane), but it is difficult to devise an inexpensive and reliable arrangement for having both the hoist and the track on which it rides reliably return to a charging station.
Owing to the foregoing problems, there has long been interest in development of a hoist which receives (or is capable of receiving) power at all times, regardless of its position along the track, and without the need for umbilical cables, and which is suitable for use in moving-track systems. One possible solution that might be contemplated is to have the track (or a portion thereof) conduct power to the trolley, which could in turn power the hoist, in a manner similar to the way in which a “third rail” powers an electric train and the components therein. However, the arrangements used in trains and the like are not reliably and inexpensively reproducible on the scale of a hoist, since hoists use substantially smaller tracks (which tend to travel along paths having substantially sharper radii of curvature than train tracks and the like). A key difficulty is in maintaining a reliable conductive connection between the trolley and track, particularly when the trolley travels about a curve in the crack; at this time, the contacts between the trolley and track are more likely to disengage, causing loss of power to the trolley in hoist systems.